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April 2009: Oobleck

Oobleck

Children love exploring gooey substances! And no wonder- the properties of these mixtures make them fascinating for children to play with!

Has your child ever played with an oozy ‘liquid’ that they can also roll into a ball? The Oobleck activity allows children to experience a material that can act in a variety of ways, depending on how it’s touched!

Playing with Oobleck is a fun way for children to explore the properties of a substance (a “non-Newtonian fluid”) that can exhibit the properties of both a liquid and a solid.

When exploring Oobleck, children and adults alike can combine what they already know and understand about materials with what they observe while playing to draw conclusions about this strange, new substance. Oobleck challenges kids’ and adults’ perceptions about states of matter, as they explore this unique substance using their senses of sight, touch and even hearing.

During the activity children are encouraged to play with Oobleck, using their hands and a variety of plastic tools- along the way, kids discover ways to make Oobleck act like a liquid or a solid, depending on how it is manipulated. Grown-ups can then talk with their children about why we call something either a liquid or a solid, and figure out which state of matter they think Oobleck is most like.

Oobleck at Home

You can continue your Oobleck explorations at home by

Making and Exploring Oobleck

Getting Ready

Oobleck Materials List:

Smocks or Aprons

Large Bowls

Measuring Spoon

Paper Towels

Plastic Tools

Plastic Trays or Bowls

Cornstarch

Water

Making your Oobleck!

Place some cornstarch on a plastic tray. Add a small amount of water. Mix the cornstarch and water together with your fingers.

Warning: Do not add food coloring in your Oobleck mixture! The color will transfer to your hands as you play, and is very difficult to wash off.

Add water to the cornstarch until the mixture appears somewhat thicker than pancake batter. There is no real recipe for Oobleck—you just have to play with it until it feels right.

Squeeze some of the Oobleck in your hand. If it remains firm as you squeeze it, but returns to a liquid form when you let go, the Oobleck is just right!

The mixture will dry as you play with it. You can add more water to bring the Oobleck back to its original state.

Try making a ball out of the Oobleck and see if you can pass it to another person before it oozes away!

Special Clean-up Instructions!

Warning: Do not pour your Oobleck down the sink! If you do, the drain may clog. Dispose of Oobleck in a trash can, carefully scraping as much as you can into the trash. Use lots of water to rinse tools and containers that you used while playing.

To clean your hands and smaller tools, fill a large bowl with water. Rinse your hands and other materials in this bowl. Then let this bowl set over night. The cornstarch will settle at the bottom of the bowl. Once this happens, you can pour the water out. Finally, dump any remaining Oobleck into the trash and rinse this bowl with lots of water as well.

Exploring the Science Behind Oobleck!

In Oobleck, the particles of cornstarch are suspended (not dissolved) in the water, creating a ‘fluid suspension.’ This causes the mixture to sometimes act like a liquid, and sometimes like a solid.

When the Oobleck is still, the cornstarch particles, which are suspended in the water, have enough time and space to move around, causing the mixture to appear liquid-like.

In contrast, when force is applied to the Oobleck (such as pressing the Oobleck with your hand), the cornstarch particles do not have space to move. In this situation, the particles create a ‘traffic jam’, and get bunched-up , causing the mixture to act, temporarily, as a ‘solid’. When force is released, the particles have time to move out of the way from one another, and Oobleck returns to its liquid-like state. The properties of Oobleck are similar to those of quicksand.

Most fluids are “Newtonian fluids”, meaning that their viscosity (that is, how quickly or slowly a liquid will flow) can be raised and lowered by changing the temperature of the fluid. Oobleck is a “non-Newtonian fluid”, meaning that its viscosity is affected by force, not by temperature. So, when you squeeze Oobleck, the substance becomes more viscous, or less fluid; and when you let go, the Oobleck becomes less viscous (more fluid).

Questions to think about:

Is Oobleck a liquid or a solid?

Can you pick up a ball of Oobleck?

What happens when you squeeze Oobleck?

Can you pour Oobleck?

What will happen when you slap your hand into a tray of Oobleck?

Fill a small cup with Oobleck. Make predictions about what will happen when you stick your fingers in it. Poke your fingers into the cup and see what happens!